A turbocharged Diesel engine system generally comprises a Diesel engine having an intake manifold and an exhaust manifold, an external air conduit for conveying fresh air from the environment into an intake line leading to the intake manifold, an exhaust line for conveying the exhaust gas from the exhaust manifold to the environment, and a turbocharger which comprises a compressor located in the intake line for compressing the air stream flowing therein, and a turbine located in the exhaust line for driving said compressor. The turbocharged Diesel engine system further comprises an intercooler, also called a charge air cooler, located in the intake line downstream the compressor, for cooling the air stream before it reaches the intake manifold, and a Diesel Oxidation Catalyst (DOC) located in the exhaust line downstream the turbine, for degrading residual hydrocarbons and carbon oxides contained in the exhaust gas. The turbocharged Diesel engine systems can also be equipped with a Diesel Particulate Filter (DPF) located in the exhaust line downstream the DOC, for capturing and removing diesel particulate matter (soot) from the exhaust gas.
In order to reduce the polluting emission, most turbocharged Diesel engine system currently comprises an exhaust gas recirculation (EGR) system, for selectively routing back a part of the exhaust gas from the exhaust manifold into the intake manifold. The exhaust gas mixed with the fresh induction air is aspired into the engine cylinders, in order to reduce the production of oxides of nitrogen (NOx) during the combustion process. Conventional EGR systems comprise an high pressure EGR conduit, also known as short route EGR, for fluidly connecting the exhaust manifold with the intake manifold, an EGR cooler for cooling the exhaust gas before mixing it with the induction air, valve means for regulating the flow rate of exhaust gas through the EGR conduit, and an Electronic Control Unit (ECU) based on a microprocessor for determining the required amount of exhaust gas to be recirculated and for controlling said valve means accordingly.
In order to further reduce the NOx emission, improved EGR systems comprise also an additional Low Pressure EGR (LPE) conduit, also known as long route EGR, which fluidly connects the exhaust line downstream the DPF with the intake line upstream the compressor, an additional EGR cooler located in the additional EGR conduit, and additional valve means for regulating the flow rate of exhaust gas through the additional EGR conduit. These valve means, in particular, are three ways valves that regulate the air flow coming from the environment air and exhaust gas recirculating flow into the engine system. While low pressure EGR conduit systems have several benefits, as explained above, they also raise the complexity of the engine structure and give rise to a certain number of technical problems. Such problems are relatively important in small Diesel engine due, for example, to the space constraints that necessarily arise in such systems.
Also, it must be considered that the three way long route EGR valve is the connection point between an air filter that filters environmental air entering into the engine system and the compressor and the long route EGR cooler, wherein the compressor and the long route EGR cooler are however rigidly fixed on the engine. Known three-ways EGR valve arrangements may comprise an air pipe having an inlet connected to the outlet of the air filter and an outlet connected to a three-way EGR valve which in turn is connected to the inlet of the compressor. This known arrangement raise the problem that high vibration arise due to the rigid connection between the three way long route EGR valve and compressor and to components downstream of the compressor. These vibrations may cause compressor cracks and fluid leakages due to high connection stresses.
At least one aim is to provide for a long route EGR valve assembly for internal combustion engines that provides a damping effect in the region between the vehicle chassis and the compressor connected to the engine thus effectively reducing vibrations. At least a further aim is to provide a long route EGR valve assembly for internal combustion engines that can be easily adapted for different engine applications. At least another aim is to meet these goals by means of a rational and low cost solution. In addition, other aims, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.